Shaft stiffening device

ABSTRACT

A golf club shaft stiffening device with a flexible tubular body including an inner circumference and a length forming a tubular cavity is described. The inner circumference of the shaft stiffening device is sized and configured to circumscribe and constrictively engage an outer surface of a shaft and to cause the shaft to have an increased stiffness characteristic, allow the location of a kick point to be modified or modify other characteristics of the golf club. The shaft stiffening device may be housed on various sections of the shaft and may be slidably adjusted or positioned on the shaft. An associated method for fitting a golf club with a shaft stiffening device is also described. The shaft stiffening devices may be provided in a kit to facilitate fitting of a golf club with appropriate shaft stiffening devices.

FIELD OF THE INVENTION

The present invention relates to a golf club accessory device, an associated golf club with the accessory device, and a method of fitting a golf club with the device. More particularly, the invention relates to a shaft stiffening device, a golf club with the shaft stiffening device and an associated method of fitting a golf club with the shaft stiffening device.

BACKGROUND

The swing of a golfer including the backswing and the downswing of a golfer is often related to the golfer's performance on the golf course. Golfers that can consistently swing a golf club in preferred manners may hit the golf ball farther, straighter and more consistently. Accuracy, control and direction may be improved when a golfer's swing has certain attributes associated with preferred swing directions, club orientations and swing motion paths. However, many golfers have difficulty swinging golf clubs according to certain preferred swing directions, club orientations and motion paths. Golfers also sometimes struggle to strike the golf ball with a golf club head in a preferred position, orientation and direction. Likewise, golf club head speed also affects the ball flight path and the distance and direction the golf ball will travel after being struck by the golf club head. Golfers vary physically in ergonomic dimensioning, strength, and other characteristics and also exhibit a wide array of variance in swing characteristics including swing speeds etc. Golf club components and golf clubs as a whole may exhibit varied characteristics based upon the characteristics of the individual components such as the shaft, the club head, and the grip. The shaft is a significant structure in performing a golf swing and may have an affect on a golfer's swing including positioning, orientation and speed of the golf club and golf club head at various points during the swing. The shaft affects performance for the club and preferred golf club performance including preferred and improved component characteristics is desirable, especially for components such as the shaft.

SUMMARY

Inventive aspects pertain to a golf club shaft stiffening device. The shaft stiffening device may be a flexible tubular body that includes an inner circumference and a length forming a tubular cavity. The inner circumference is sized and configured to circumscribe and constrictively engage an outer surface of a shaft and to cause the shaft to have an increased stiffness characteristic. The shaft may be removable. The tubular body may also be a unibody member in certain arrangements. The shaft stiffening device may be slidably adjustable on the shaft.

In another aspect, inventive aspects pertain to a golf club with a golf club head, a shaft coupled to the golf club head and housing a grip, and a shaft stiffening device slidably housed on an outer surface of a shaft such that the shaft stiffening device is external to the shaft. The shaft stiffening device may be sized, shaped and otherwise configured to constrictively engage a specific region of the shaft.

In another aspect, a method of fitting a shaft of a golf club with a shaft stiffening device is described. The method may involve determining a stiffness characteristic of a shaft of a golf club, determining a desired stiffness characteristic of a shaft based upon a swing of the golf club using a measuring device, and selecting a particular shaft stiffening device from among a plurality of available shaft stiffening devices. The selected shaft stiffening device may be placed on the shaft so it constrictively engages an outer surface of the shaft over a given region of the shaft.

In another aspect, a kit with a series of shaft stiffening devices is described. The shaft stiffening devices may have varied characteristics so as to fit varied portions of the shaft and/or varied characteristics to cause the shaft to exhibit certain characteristics when one or more of the shaft stiffening devices are constrictively engaged with the shaft.

DESCRIPTION OF THE DRAWINGS

The foregoing Summary, as well as the following Detailed Description, will be better understood when read in conjunction with the accompanying drawings.

FIGS. 1A-1B are schematic front and toe end views respectively of various arrangements of golf clubs.

FIGS. 2A-2B are illustrative diagrams depicting characteristics, including shaft characteristics of a golf club.

FIGS. 3A-3C depict side, perspective and end views of an illustrative arrangement of a shaft stiffening device.

FIG. 4 is an illustrative diagram of other arrangements of several shaft stiffening devices.

FIGS. 5A-5D are diagrams depicting illustrative effects of various shaft stiffening device, on a golf club.

FIG. 6A-6B are illustrative views of application of the shaft stiffening device to a golf club.

FIG. 7 is an illustrative schematic diagram of one arrangement of a kit of shaft stiffening device(s).

FIGS. 8A-8C illustratively depict aspects of a method of fitting a golf club and associated devices.

DETAILED DESCRIPTION

In the following description of the various embodiments, reference is made to the accompanying drawings that depict illustrative arrangements in which the invention may be practiced. It is understood that other embodiments may be utilized and modifications may be made without departing from the scope of the present invention.

FIGS. 1A-1B are schematic front and toe end views respectively of three arrangements of a golf club 199. The three arrangements may be commonly referred to as an “iron,” a “driver” and a “hybrid” golf club 199. This terminology is known by those skilled in the art. The driver and the hybrid golf clubs 199, while having distinctions between them including size of the golf club head, shape and loft, among other potential illustrative potential distinctions, both may be classified more generally as “wood-type” golf clubs with wood-type golf club heads. Fairway woods, rescue clubs, numerically referenced woods, such as 3-wood, 5-wood, 7-wood and other terminology also refer to golf clubs that may characterized as “wood-type” golf clubs. The iron 199 may generally be described as an “iron-type” golf club with iron-type golf club heads. Long, medium and short irons (or numerical irons such as 3-iron, 7-iron, 9-iron etc.) may be considered iron-type golf clubs. Also, various wedges such as loft wedges, sand wedges, pitching wedges and gap wedges may also be considered “iron-type” golf clubs. Putters and other types of golf clubs also exist and are known in the art.

As is apparent from the figures, a golf club head 100 may illustratively be considered to include top 110, front 120, toe end 130, rear 140, heel end 150 and bottom (or sole) 160. Further, a golf club head 100 typically includes a hosel 180 formed to, among other things, facilitate connection of the golf club head 100 to the shaft 190. Depending on whether the golf club 199 is a “wood-type” or an “iron-type” golf club, the golf club head 100 may have a varied configuration and the size, material, shape, and other characteristics of the above described portions will be varied as is known in the art. Hosels 180 are commonly formed along with the remainder of the golf club head 100 and is the portion of the golf club head 100 that typically couples the shaft 190 to the golf club head 100. The hosel 180 design may affect the balance, feel, and power of the club. However, a hosel 180 generally is not considered in detail by an end consumer of golf equipment and more typically are considered by golf club designers and manufacturers, and like entities. The primary function of hosel 180 may be to couple the shaft to the remainder of the golf club head 100, however, hosel 180 configured with certain shapes, sizes, orientations and coupling orientation and angles may provide the golf club 199 with desirable traits including placing a minimal amount of mass above the top of the front surface 120 of the golf club thereby providing the club with a lower center of gravity and thereby facilitating the golfer in hitting a golf ball a further distance.

Front surface 120 typically houses a hitting surface 125 configured for striking a golf ball. Hitting surface 125 may include any of a variety of features, configurations, shapes, surfaces and details. For example, hitting surface 125 may include a series of horizontal grooves that facilitate desired flight of the golf ball when the hitting surface 125 impacts a golf ball. Spacing, size, depth, shape, contour and orientation of these grooves may be varied based on club type (and/or particular club manufacturer) to achieve a desired ball flight characteristic. Many other forms of surface treatments and ornamentation may be incorporated into the hitting surface 125, from hardened materials to holes, grooves, and corrugation and various other hitting surface materials, structures and configurations that are well known.

The shaft 190 of a golf club 199 is an elongated member typically made of steel or graphite that connects the golfer's hands to the golf club head 100. The golfer often holds the golf club 199 by holding or gripping the grip 195 housed on an end off the shaft 190 opposite the golf club head 190. Among the functions of the golf club shaft 190 is to facilitate a golfer to hit or strike a golf ball to make the golf ball travel in a desired travel path and distance. The shaft enables the golfer to strike the golf ball as the configuration of the golf club 199 including the configuration and characteristics of the shaft 190 enable and facilitate the golfer to generate a centrifugal type force which is applied to the golf ball through the golf club head 100 and to the golf ball when the golf club head 100 strikes the golf ball. Shafts 190 may vary in their particular dimensioning especially their length but also in other characteristics such as diameter. Often the shaft 190 is a tapered tube. In one configuration the shaft has a diameter of approximately one half inch near the grip and continuously tapers down the length of the shaft until the end opposite the grip 195 (the end is housed in the hosel 180) will generally be at its narrowest with a diameter smaller than the diameter near the grip (e.g. less than 0.5 inches).

Shaft 190, as is also known in the art, may be varied in length, material composition, stiffness, flex and other traits and features. For example, golfers may select shafts formed of a variety of materials in light of characteristics of those materials. One characteristic of shafts 190 is its composition material. Generally, modern shafts for golf clubs are composed of either steel or graphite. Steel shafts generally are heavier and have a lower torque rating than graphite shafts. Steel is generally more durable and resistant to damage than graphite as well. Conversely, graphite is generally lighter and has a higher torque rating and torque range available to choose from depending on the particular graphite selected. Early graphite shafts were often made with a single layer of composite fibers which sometimes hampered performance by allowing shaft flexure. Modern graphite shafts often have three layers of wound fiber which provides increased rigidity and performance. Among the more common graphite shafts are those made by various shaft manufacturers including Fujikura, UST, Grafalloy, Mitsubishi, Aldila as well as other known manufacturers. Both steel and graphite shafts are known including the particular steel(s) and graphite(s) utilized in shafts for golf clubs 199.

Additionally, flex and stiffness are among the illustrative characteristics that may be contemplated when selecting a particular shaft or shaft material as a preferred shaft stiffness may vary from golfer to golfer depending on skill, strength and swing characteristics including swing speed or swing path. Flex is the measure of the shaft's flexibility. A measurement of flex may be a relative measurement. Stiffness is a measure of how much deflection occurs in a shaft for a given tangential force applied to the golf club head 100 (e.g. the face or hitting surface 125 of the golf club head 100). An illustrative demonstration of varied shaft stiffness between two golf clubs substantially identical except for different shafts may be performed by clamping an end of the golf club opposite the golf club head so as to hold the golf club in a fixed immobile position capable of supporting a weight. Then a given weight may be hung from the end of the golf club with the golf club head. In particular, the weight may be applied to or hung from a front surface of the golf club head. With one end being clamped securely and a weight hanging from the opposing end of the golf club 199, the golf club will form a cantilever member. However, the shaft will not remain rigid but instead will exhibit a bend that increases as one moves closer and closer to the location at which the weight is hung from the golf club 199 such that the golf club head may be described as bowing much as a fishing rod bows when a force is applied to an end opposite the end in which the user is firmly gripping the fishing rod. Now, the same demonstration may be performed with the second golf club 199 that is substantially identical except the shaft exhibits a stiffer shaft. Here, the second golf club used in the demonstration will not bow or bend to the same extent as the first golf club due to the increased stiffness characteristics of the shaft 190. Described from another perspective if two given shafts only vary in their stiffness, more force needs to be applied to the stiffer shaft to cause the shaft to deflect or bow to the same magnitude as the less stiff shaft (see FIG. 2B).

The above illustrative demonstration may be associated with a golfer's swing. As the golfer begins a downswing, the golfer will begin bring their hands which are gripping the golf club 199 at the grip 195 and the shaft 190 will exhibit a bend as the golf club head 100 initially trails behind the golfer's hands at the beginning of the downswing. The golfer's hands are driving the shaft 190 (and the golf club head 100 at the opposing end of the shaft) around the golfer 10, but the shaft 190 lags a bit. However, the shaft lag results in energy being stored in the shaft 190 in the form of a bend in the shaft. Now, as the golfer continues the downswing, the shaft 190 will continue to bend further to the extent its physical stiffness characteristics permit it to bend further. At a certain point the shaft 190 will reach its maximum bend based upon its stiffness compared to the speed of the golfer's swing and then the shaft 190 will begin to release its stored energy and begin to straighten out. In certain instances it may be preferred for the shaft 190 to reach its maximum bend as a golfer's left elbow begins to straighten out (assuming a right handed golfer). As mentioned above, at this point, the shaft 190 will begin to straighten out thereby causing the golf club head 100 to increase in velocity. As is recognized, increased club head velocity at the time the club head 100 impacts the golf ball will directly result in the golf ball having an increased initial velocity which will causes the ball to generally travel farther, as is often desirable in the game of golf. In order to maximize or optimize the velocity of the golf club head 100 at the time of impact of the hitting surface 125, the shaft 190 can be configured or chosen so that it will finish straightening out simultaneous with impact of the golf club head 100 with the golf ball. Generally, the golf club head 100 will be moving at a maximum velocity of the swing simultaneous with the shaft 190 straightening as all of the energy stored as potential energy in the bend is released. However, if the golf club head 100 (and shaft 190) continues to travel for a certain distance/time after the shaft straightens out before the golf club head 100 impacts the golf ball, energy will be lost as energy begins to be stored by the shaft 190 bending again but in the opposite direction as during the initial downswing. Accordingly, it is desirable for the shaft to consistently straighten as the golf club head 100 impacts the golf ball.

Thus a golfer may desire to have a golf club 199 with a shaft 190 that will straighten out at the moment of impact to optimize the force that their swing is generating and accordingly will maximize the distance the golf ball travels. Accordingly, the golf club head 100 will be moving as fast as possible for the given golfer's swing etc. Therefore, a shaft 190 will often be chosen to accomplish the optimized timing and straightening out of the shaft 190 as described depending on the golfer's swing characteristics. For example, if a golfer has a very fast swing but has a golf club with a supple shaft, the golfer's shots will not travel as far as they possibly could be travelling if the golfer was optimizing his swing energy because the shaft 190 has absorbed energy in the form of a bend in the shaft 190 and will not have fully released what it previously stored at the moment of impact and golf club head 100 velocity at impact will not have been maximized. Swing energy will have been wasted and the resulting shot will not achieve maximum travel distance. On the other hand, if a golfer has a slow swing but selects a very shift staff, a similar shot inefficiency and failure to maximize swing energy will result but for the opposite reason. In this instance the shaft will straighten out while the golfer is still in the downswing and the golf club head will travel ahead of the shaft such that the shaft is now bent forward. Again, the bent shaft at impact equates to wasted swing energy and a slower golf club head 100 velocity at impact. Again, the golf ball's travel distance after impact will not be maximized. As such, it is desirable for a golfer to have a golf club 199 that includes a shaft with complimentary stiffness characteristics to the golfer's swing to maximize the golfer's swing and swing energy and optimize the golfer's shots. Premature or tardy straightening of the club shaft 190 may also cause the directional aspects of the golf shot to be significantly altered as the orientation and travel path that the golf club head 100 takes as it travels through the hitting zone and contacts the golf ball can be varied. Accordingly, the golf ball may not be struck in a sweet spot of the hitting surface. Also, the golf ball may take an initial direction path askew from the desired path of travel. Spin may also be placed on the ball so as to inadvertently cause the golf ball to travel with a “hook” or “slice” path of travel. Further, the struck golf ball may not travel with an initial desired ball flight angle relative to the ground such that the ball is “popped up” or skulled and hit so as to skim the ground rather than travel with an elevated loft through the air such that the vast majority of the ball's travel distance occurs while the ball is traveling in the air rather than during rolling, bouncing or skimming the surface of the ground.

Another characteristic that may be considered when selecting a golf shaft 190 for a golf club 199 is the bend point or kick point 205. The bend point or the kick point 205 is the location over the length of the golf club 199 where the club is defined, configured and/or arranged to bend. Various shaft models may be designed to have a kick point 205 at various respective locations along their length. In some instances a shaft 190 may be generalized as having a low, mid or high kick point 205. The kick point 205 of a shaft 190 will often affect the orientation of the golf club head 100 when the golf club head 100 strikes the golf ball 201. Accordingly, the location of the kick point may vary shot tendencies. Accordingly, a golfer may choose a golf club with a kick point 205 in a particular location to complement his or her swing tendencies, swing speed and golf skill. Generally speaking, a shaft 190 with a high kick point 205 (near the grip 195 end of the golf club—e.g. 205B in FIG. 5B) will produce lower launching and lower spinning golf shots. Often more skilled lower handicap golfers will desire these characteristics as the more skilled golfers desire to maximize distance and accuracy on their golf shots. These golfers typically are consistently able to hit the ball in the air and do not have trouble making solid contact with the ball. Rather, these golfers tend to desire improved distance and accuracy to allow them to more accurately “place” their golf shots and to maximize the power and distance of their swings. In contrast, a low kick point 205 (e.g. 205D in FIG. 5D) may be especially desirable to less proficient and high handicap golfers as these golfers may have a tendency to have difficulty striking the golf ball and may struggle to “get the ball in the air.” Accordingly, a golf club shaft 190 with a low kick point 205 near the club head end of the golf club 100 will typically produce higher launching, higher spinning golf shots. As is known, high launching (or popped up) golf shots may result in the golf shot not maximizing distance of the golf shot. Also, increased spin may result in less accuracy of the golf shot and the ball may travel left or right of the desired travel path (respectively being hooked or sliced for a right handed golfer). However, these less proficient/high handicap golfers may struggle in getting the ball “up in the air” especially with certain clubs with less loft including high or long irons or certain woods including drivers, 3-woods etc. Because a shot in which a golfer does not get the ball “up in the air” may be a “duff” or a wasted shot, the less proficient golfer will often desire to sacrifice some distance by having a higher ball flight in exchange for a reduced frequency of waste or duffed shots in which the golfer does not solidly strike the ball or fails to launch the ball with sufficient trajectory to get the ball to travel in the air a significant distance. A golfer falling between these two ranges of skills may accordingly desire a mid kick point 205 (e.g. 205A in FIG. 5A) that falls in the middle of the golf club and exhibits blended or average tendencies of the mid and low kick point shafts. While generally golfers may select shafts 190 with kick points 205 at locations based upon the above described criteria, golfers may also rely on “feel” or personal preferences to select shafts 190 with characteristics in a manner counter to that described above. For example, a less proficient high handicap golfer may select a shaft with a high kick point 205B while a highly proficient golfer may select a shaft with a low kick point 205D despite the above tendencies and generalizations.

Since each golfer's swing may be varied, golfers will have varied preferences regarding the shaft 190. In at least one categorization system, shafts may be categorized by stiffness as Extra Stiff (X), Stiff (S), Regular (R), Senior (A) and Ladies (L) depending on the particular flex characteristics. However, no uniform industry standard exists with respect to stiffness of the shaft and a shaft categorized as “Stiff” by one shaft manufacturer will in certain instances possess the same or similar stiffness characteristics as a “Regular” shaft by another shaft manufacturer. Regardless, generally speaking, golfers generally may select a shaft based upon the distance they may typically hit a golf ball with a given club. For example, golfers and golf professionals may look to the distance that a golfer hits a drive with a driver as a guide in selecting a shaft stiffness. If a golfer hits a driver further than 250 yards they may desired a Stiff shaft; 230-250 yards—Regular shaft; 200-230 yards—Senior shaft; less than 200 yards—Ladies shaft. Extra Shift shafts are typically not used except for professionals, extremely low handicap, or extremely strong and fast swinging golfers. Again, these characterizations are merely illustrative generalizations and each golfer may desire a given golf club with a given shaft that exhibits preferred characteristics including shaft stiffness, length 290, kick point 205 location and various other traits as desired.

The golf club 199 typically includes a shaft 190 coupled to the head 100 at the hosel 180. A grip 195, at which a golfer holds or grips the golf club, is attached to the shaft 190 at the end opposite the head 100. Grips 195 are known and may vary significantly depending on preferences, ergonomic characteristics, and tendencies of the golfer, such as a tendency to hit slice or fade. For example, grips vary in “grip size” and in circumference. They also vary in particular texture and grip pattern on the outer surface of the grip. Grips can be round or may have a line or rib on the underside to assist the golfer in placement of his hands. Other shapes are also contemplated. Grips may be composed of a number of materials including rubbers, polymers, and leather, to name a few. The grip traits may be varied by, for example, making the grip corded or selecting any of various materials based upon the frictional properties of that material.

FIGS. 2A-2B are illustrative diagrams of golf club 199 demonstrating varied shaft stiffness and kick points 205A-E of a golf club. FIG. 2A illustrates the flex characteristics of a golf club configured with 5 different stiffness characteristics consistent with the principles discussed above. As such, the golf club 199 and in particular the shaft 190A-E may exhibit a state of maximum flex as shown and will be orientated with each arrangement of the golf club 199 to have a respective maximum flex 255A-E associated with the five respective shafts 190A-E of varied stiffness. For example, the shafts 190A-E may illustratively be shown in the state of maximum flex may be illustrative described as Extra Stiff Shaft 190A, Stiff Shaft 190B, Regular Shaft 190C, Senior Shaft 190D, and Ladies Shaft 190E. These designations are again illustrative and for ease of understanding and clarity, however, they may vary greatly. For example, in another arrangement the same five shafts 190A-E illustrated in maximum flex state may all be characterized or labeled as “Regular” shafts and may have varied specific stiffness characteristics despite all being characterized as “Regular” shafts. Shaft 190A may be characterized as the stiffest shaft, shaft 190E as the least stiff and shafts 190B-D falling in line accordingly in between shafts 190A and 190E with respect to stiffness. Also shown in FIG. 2A is a flex length 290 which is equivalent in this arrangement the length 210 of the golf club and/or shaft which may be flexed when force is applied to the golf club 199. Also, the golf club 199 and each of the five arrangement of the golf club 199 with varied shafts 190A-E are shown as having the same kick point 205 where the shaft bends as shown. While these shafts 190A-E have a common kick point 205, varied locations of kick points 205 between shafts 190A-E with varied stiffness is contemplated and will be described in further detail later.

FIG. 2B further illustrates the effects of a golf club shaft for a given golf club 199 having a varied stiffness. FIG. 2B illustratively depicts golf club 199 clamped at the grip end 195 of the golf club 199. The clamp 299 (drawn for illustrative purposes as a golfer's grip) securely holds the grip 195 and the portion of the shaft 190 housed within the grip in a rigid fixed position. As such the region of the shaft housing the grip 195 and held in the clamp does not exhibit flex or bending when a force in the form of a weight 260 hung from the opposing club head 100 end is applied. The golf club 199 is again shown with a series of 5 shafts 190A-190E shown in a flexed stated as a result of the force in the form of weight 260 being applied as described. Here, because the grip end 195 of the golf club is clamped and does not exhibit flex or bending, the flex length 290 and the actual length of the shaft are different. As such, the flex length 290 of the golf club 199 illustratively shown in FIG. 2B is the length 290 running from one end of the grip 195 to the opposite end of the shaft 190 at the golf club head 100.

Variances in the behavior of the golf club 199 between arrangements of varied shafts 190A-E with varied stiffness are shown. Again, shaft 190A is the stiffest shaft while shaft 190E is least stiff with the other shafts shown falling accordingly and respectively in line. As is apparent from FIG. 2B, the stiffer the shaft 190 is the less deflection or bending the shaft 190 exhibits when a given force 160 is applied at a given location. Further, the illustrative diagram of FIG. 2B illustrates that the location of a kick point 205 may be varied as well between shafts 190 including especially including shafts 190A-E with varied stiffness. Here, shaft 190A has the lowest kick point 205A, shaft 190E has the highest kick point 205E, and shafts 190B-D have associated kick points 205B-D falling in between. In this instance the variance in particular location of kick point 205 location is minimal as compared to the respective lengths of the flex length 290 and length 210 of the golf club 190. A given golf club shaft 190A-E may be made with a certain given stiffness characteristic and kick point 205A-E. However, it may be preferred for the stiffness of the shaft 190 to be varied, or the location of the kick point 205 be varied. Further, it may be desirable to vary the stiffness of only a portion of the shaft 190 while maintaining the original stiffness of the remainder of the shaft 190. For example, by stiffening a portion of the shaft 190 but allowing the remainder of the shaft to continue to exhibit the original stiffness characteristic, more customized stiffness, kick point and related characteristics may be achieved as desired. For example, overall stiffness may be varied, and/or the locale of the kick point 205 may be transitioned. Specifically, the kick point 205 may be shifted either further up the shaft 190 towards the grip 195 such that the kick point 205 is higher and the golf club 199 has a tendency to provide higher launching trajectory/ball flight when the golf club 199 is used or further down the shaft 190 such that the golf club 199 will has a tendency to provide a lower launching trajectory/ball flight. By varying the stiffness of the shaft 190 in certain regions, the kick point may be resultantly shifted as well as the flex length 290 of the shaft 190 may be varied thereby causing the location at which bend occurs to be varied.

FIGS. 3A-3C depict side, perspective and end views of one illustrative arrangement of a shaft stiffening device 300 housed on a cut-away portion of a shaft 190 of a golf club 199. This configuration of shaft stiffening device 300 shown in FIGS. 3A-3C includes an elongated tubular body 310 with two hollow opposing ends 311, 312. The shaft stiffening device has a length 330 running from one end 311 to the other end 312. The opposing ends 311, 312 have respective inner circumferences 321, 322. The shaft stiffening device is hollow radially inward between the inner circumferences 321, 322. As such, the shaft stiffening device 300 houses a hollow cylindrical channel running (not shown as it is filled by the shaft 190 in FIGS. 3A-C) between opposing ends 311 and 312. The channel is configured to house and constrictively engage a shaft 190 of a golf club 199. As such, the shaft stiffening device 300 is fit snugly around the shaft 190 while not being so snug on the shaft so as to prevent the shaft stiffening device 300 from being slidably adjustable and maneuverable on the shaft 190 of the golf club 199. The shaft stiffening device 300 may be adjusted to a specific desired position on the shaft 190. The opposing ends 311, 312 may have inner circumferences 321, 322 of the same size or the inner circumferences may be varied in size to further compliment a tapered shape including common shapes such as a continuously tapering rounded shape of a shaft 190 of a golf club 199.

The shaft stiffening device 300 may be formed of a variety of materials including various plastics, rubbers, elastomers and various other materials known. To allow the shaft to be applied to the golf club shaft 190 the shaft stiffening device 300 may be formed of flexible material that when applied over the top of another surface of the shaft 190, the shaft 190 in that region exhibits increased stiffness. For example, in one illustrative example the shaft stiffening device may be composed of longitudinal tape formed to have increased stiffness in the longitudinal direction running up and down the shaft 190. In another illustrative example, the shaft stiffening device may be a polymer or plastic. Numerous other materials and combinations of materials may be used in the shaft stiffening device consistent with that described herein. Should the staff stiffening device 300 be applied over the grip 195, the material will need to be flexible to allow the device 300 to expand over the grip 195 and still constrictively engage shaft 190. As will be described in more detail in relation to FIG. 6, the shaft stiffening device may be placed over the shaft prior to complete assembly of the golf club 199 including prior to attachment of the golf club head 100, the grip 195 or both. In arrangements in which the shaft stiffening device is placed over an exterior surface of a shaft 190 prior to complete assembly of the golf club 199, more rigid and less elastic materials may be utilized than might be possible should the shaft stiffening device need to be slid over a grip or other portion of the golf club head having a larger circumference (perimeter) than the shaft 190 (e.g. grip 195). Change or replacement of grips 195 of a golf club is a common practice. As such, removal of a grip 195 to apply the shaft stiffening device 300 is known to be a simple practice such that even in configurations in which the shaft stiffening device 300 is configured (including being composed of sufficiently elastic materials) such that the shaft stiffening device may be stretched and pulled over an obstructing portion of the golf club 199, it may be desirable to remove the grip 195 of the golf club. However, as described certain configurations of the shaft stiffening device 300 are configured such that they may applied to an assembled golf club 199 after market with out disassembling any portions of the golf club 199. As such, when a golfer learns after purchase and/or use of a golf club 199 that different shaft characteristics may be more complimentary to his/her swing, the shaft stiffening device 300 may be applied and the shaft characteristics potentially including increased overall shaft stiffness, increased stiffness of portions of the shaft or shifting of the kick point 205 of the golf club 199.

The shaft stiffening device 300 may constrictively engage the outer surface of the shaft 190 as the inner circumference 321, 322 of the shaft stiffening device 300 in a non-engaged state will be smaller than the outer surface of the shaft 190. When the shaft stiffening device is pulled over the outer surface of the shaft 190 the structural integrity of the shaft as a solid steel or graphite material will retain its shape and size. As such the shaft stiffening device 300, to the extent its material properties are such that permit a certain amount of expansion and “stretch” in the radially outward direction, including the inner circumference running between and including inner circumferences 321, 322 will be expanded thereby stretching a portion of the shaft stiffening device 300. The shaft stiffening device will be placed under expansion stress force and will exert an opposite force upon the outer surface of the shaft 190 as the integrity of the material of the shaft stiffening device 300 resists deformation. These opposite forces cause the shaft stiffening device 300 to constrictively engage the shaft 190. The shaft stiffening device 300 is configured such that it will be able to withstand the forces applied during a golfer's swing and will remain in the specific location it has been placed. In short, the force up and down the club shaft 190 during a swing are not greater than a resistive frictional engagement force as a result of the shaft stiffening device 300 being constrictively engaged with the outer surface of shaft 190. However, the shaft stiffening device 300 is also configured such that if a golfer 10 or other user applies a sufficient direct force to an end 311, 312 and/or the outer surface 340 of the shaft stiffening device 300, the shaft stiffening device 300 will slide a certain distance in one or both directions on the shaft 190. In certain configurations the shaft stiffening device 300 may be slid across the entire length of the golf club shaft 190 or at least between the hosel 180 and the bottom of the grip 195. In other configurations, a shaft stiffening device 300 may be more specifically configured such that it may be adjusted within a certain region (e.g. 400A-C) of the shaft, however, it will not be slidable to any location on the shaft, just adjustable within one of a low 400A, mid 400B, or high 400C section of the shaft 190. (See FIGS. 4 & 5A-5D).

FIG. 4 is an illustrative diagram of several arrangements of a shaft stiffening device 300. For reference, the shaft of a golf club 199 may have a low section 400A, mid section 400B, and a high section 400C. The low section 400A as shown is the section of the shaft adjacent to the golf club head 100 (and hosel 180 to the extent the particular arrangement of the golf club 199 includes a hosel). The low section 400A is the portion of the shaft 190 that typically has the smallest circumference diameter especially when the shaft 190 is continuously tapered from the grip end 195 to the club head end 100 on the opposing end of the shaft 190. The high section 400C is the portion of the shaft 190 that is adjacent to the grip end 195 of the golf club 199 while the mid section 400B is the section between the low section 400A and high section 400C. The shaft stiffening device 300 may be specifically configured and sized for one of the low section 400A, mid section 400B, or the high section 400C. The specific sizing allows the shaft stiffening device 300 to be more specifically tailored to each section 400A-C including length and circumference. As shown, shaft stiffening devices 300A, 300B, and 300C are respectively sized, shaped and formed to constrictively engage sections 400A, 400B, and 400C respectively of the shaft 190. In at least one arrangement, shaft stiffening devices have a length 330A, 330B, 330C that is shorter than the length of section 400A, 400B, 400C, respectively, of the shaft.

Since the shaft stiffening device 300A, 300B, 300C is shorter than its corresponding section 400A, 400B, 400C on the shaft 190, the shaft stiffening device 300A, 300B, 300C may be slidably adjusted with section 400A, 400B, 400C so as to finely adjust the shaft stiffness altering affect of the shaft stiffening device 300 including the specific portion of the shaft 190 caused to be stiffened or a shifted location of the kick point 205 to occur.

FIGS. 5A-5D are illustrative diagrams depicting an illustrative affect the shaft stiffening device 300A-300C has on the golf club shaft and the flex, stiffness, and kick point attributes. FIG. 5A illustratively depicts a golf club 199 without any shaft stiffening devices 300A-C. Also, in FIG. 5A the golf club 199 has a flex length of 290A shown as extending from the golf club head 100 to the grip 195. Similar to how the portion of the shaft 190 with the grip 195 did not demonstrate bend or flex in FIG. 2B, the grip 195 also will generally remain straight and rigid. Also, similar to how the grip 195 was clamped in place and thus did not bend, the golfer will grip the golf club on the grip 195 and the golfer's hands will act as a securing force (like the clamp) preventing the shaft from bending at the grip 195. It should be understood and recognized that golfers may grip the shaft at varied positions on the grip 195 and thus the flex length 290 may actually include portions of the lower end of the grip 195, however, for illustration and explanation purposes FIGS. 5A-5D assume the grip 195 is held rigid by outside forces such as by a golfer's hands down the entire length of the grip 195.

FIGS. 5B-5D illustratively show the golf club 199 with a shaft stiffening device 300A-300C housed on the low 400A, mid 400B, and high 400C sections of the shaft 190. FIGS. 5B-5D also demonstrate the effect shaft stiffening devices 300A-300C have on various golf club 199 characteristics including flex length 290B-290D and the location of the kick point 205B-205D. FIG. 5B illustratively shows the golf club 199 with shaft stiffening device 300A housed on the low section 400A of the shaft 190 adjacent to the golf club head end 100. The shaft stiffening device is constrictively engaged about the exterior of the shaft 190. The stiffening device 300A may be composed of a number of materials as described previously including rubbers, polymers, plastics and other materials. The shaft stiffening device 300A constrictively engaging the low section 400A of the shaft causes the region portion of the shaft radially inward of the shaft stiffening device to exhibit an increased stiffness characteristic down the length 330A between the ends 311A, 312A of the shaft stiffening device 300A. Here, the stiffness characteristics have been altered such that the shaft 190 is rigid in the low section 400A of the shaft of the golf club 199. Accordingly, the portion of the shaft that exhibits flex or bending can be changed as can the associated flex length 290B. Additionally, the kick point 205B is shifted upward further towards the high section 400C and the grip 195 of the golf club. FIG. 5C illustratively shows the golf club 199 with shaft stiffening device 300B housed on the mid section 400B of the shaft 190 of the golf club head 100. Similarly, the shaft stiffening device 300B is depicted through its constrictive engagement as causing the mid section 400B to exhibit increased stiffness characteristics and in particular fairly rigid characteristics. Accordingly, the shaft 190 now has two flex length regions 205C. Additionally, the shaft in the configuration of FIG. 5C also has a pair of kick points 205C on opposite sides of the shaft stiffening device. Lastly, FIG. 5D illustratively shows the golf club 199 with shaft stiffening device 300C housed on the high section 400C of the shaft 190. The high section 400C of the golf club shaft is shown as having an increased stiffness trait as the shaft in this region is illustrated as being held generally rigid by the shaft stiffening device 300C. Accordingly, flex lengths 290D extend down near golf club head 100 end of the golf club head 100 and at the grip 195 respectively. Also, the kick points 205D have varied locations.

As shown and described, the shaft stiffening device 300A-300C can be formed in various flexible yet constrictively engaging structures that compress down on the shaft in a particular region. As such, the shaft 190 can be further supported and the shaft in that particular region will exhibit increased stiffness characteristics. The extent to which the stiffness characteristics are varied will depend on various characteristics potentially including the original shaft stiffness, the length of the shaft stiffening device 330A-330C, the material composition of the shaft stiffening device 300A-300C, the snugness of the constrictive engagement by the shaft stiffening device 300A-300C, swing characteristics of the golfer 10 and other specific characteristics. Also as shown, the shaft stiffening device 300 may be further formed to engage the shaft 190 so as to modify the shaft characteristics as desired without altering other features of the golf club 199. For example, to provide a continuous and smooth feel to the golfer, when a shaft stiffening device 300C is specifically configured for the high section 400C of the shaft, the shaft stiffening device 300C may be formed in one arrangement such that end 312 abuts the lower end 196 of the grip 195 such that an outer surface of the grip 198 is flush with the shaft stiffening device 300C. As such, the shaft stiffening device 300C when positioned as shown provides the feel of a single elongated grip 195 rather than a distinct structure near the top of the shaft 190. As such, improved feel characteristics may be accomplished while still accomplishing the shaft characteristic altering function as desired.

While the regions of the shaft 190 within the shaft stiffening device(s) 300 are shown as exhibiting no flex for illustrative purposes in the diagrams of FIGS. 5A-5C, the shaft 190 in these regions may exhibit reduced flex rather than no flex in various configurations. As such, the shaft characteristics including shaft stiffness characteristics may be accomplished consistent with that described herein as the “reduced flex” regions will have similar effects as “no flex” regions on the characteristics and functionality of the shaft, perhaps with just variances in degrees and extent of certain characteristics. Likewise, while the region of the shaft 190 within the grip 195 is shown as having a flex region in FIGS. 5A-5D, this region will likely have a reduced flex characteristic (or no flex) as a result of the golfer gripping this region with his hands when swinging the club in the configurations of FIGS. 5A-5D as the golfer's hands may act as a clamp consistent with that shown in FIG. 2B.

FIG. 6A illustratively depicts one arrangement for placing a shaft stiffening device 300 on a shaft 190 of a golf club 199. In this arrangement of the golf club is shown as three sections, the golf club head 100, the grip 195, and the shaft 190. These three sections are coupled together to form the golf club 199. Application of the shaft stiffening device 300 is more easily performed prior to the golf club 199 being constructed. As shown in FIG. 6A, if the golf club 199 has not yet been completely constructed such that one or both the grip 195 and/or the golf club head 100 has not been attached to the remainder of the golf club 199, the shaft stiffening device 300 may be pulled onto the shaft 190 and slid to the desired position. In certain arrangements it may only be possible to apply the shaft stiffening device 300 from only one of the ends as the tolerances may be sufficiently tight such that the shaft stiffening device could not be slid up the length of the shaft as the wider diameter of the shaft encountered during the slide would cause the shaft stiffening device 300 to become stuck. In the arrangement of FIG. 6A, the shaft stiffening device 300 is applied to the shaft and positioned in the desired location. Next, the golf club head 100 and the grip 195 will be accordingly coupled to the shaft 190 using securing processes and adhesion techniques and adhesives as are known in the art. Alternatively, as described previously, certain configurations of shaft stiffening devices may be applied in retro fit to a fully constructed golf club 199. Typically in such a retrofit situation, if the golf club 199 is not going to be disassembled to any extent the shaft stiffening device will be applied over the grip 195 and slid further down shaft 195. Alternatively, as shown in FIG. 6B the shaft stiffening device 300 may be formed such that the shaft stiffening device 300 is an arrangement of two split halves 610, 620 in one configuration the halves may be equivalent in size and shape such as true halves or they may be varied in size and shape. The halves 610, 620 whether similar shaped in size or varied can be fit together such that the halves 610, 620 form a shaft stiffening sleeve that wraps around the shaft 190 and snaps, is pressure fit, or is otherwise held together once constrictively engaged with the shaft 190. Among the mechanisms that may be utilized are snap fits, compression fits, bonding, adhesives and various other techniques for holding two structures and/or two materials together. FIG. 6B illustrates a snap fit in which a metal connector(s) 611 is housed on half 610 and thereby engages and connects to half 620 which has complimentary female connector(s) 612. While shown and described as halves, it is understood that a shaft stiffening device 300 may be composed of three, four or more structures of the same or varied shapes and sizes so as to form a structure for constrictively engaging the shaft 190 consistent with that described herein. These illustrative connections shown are merely illustrative and many other specific connection arrangements and configurations are contemplated.

FIG. 7 is an illustrative schematic diagram of one arrangement of a kit 700 of shaft stiffening device(s). Here the kit 700 includes a series of shaft stiffening devices 300A, 300B, and 300C. Each of the shaft stiffening devices 300A, 300B, 300C is specifically formed for a specific portion of the shaft 190. Here, shaft stiffening device 300A is sized and shaped to specifically fit the low section 400A of the shaft, shaft stiffening device 300B is sized and shaped to specifically fit the mid section 400B of the shaft, and shaft stiffening device 300C is sized and shaped to specifically fit the high section 400C of the shaft. Because of the specific characteristics of the shaft, the shaft stiffening device 300A-300C vary in cross-section and length with shaft stiffening device 300A being the shortest and having the smallest cross-section while shaft stiffening device 300C is the longest and has the largest cross-section. In this particular configuration, kit 700 includes a housing 750 configured to house three shaft stiffening devices 300A, 300B, 300C in visible holders 710A, 710B, 710C. The kit 700 and housing 750 in particular can be hung on a shelf or otherwise viewed, displayed and suspended for viewing, selection and/or purchasing. The kit 700 may be utilized akin to a club testing cart such that the a plurality of shaft stiffening devices 300 may be housed in the kit and golfers, golf professionals, and potential purchasers may view and select shaft stiffening devices from a series of shaft stiffening devices available for testing. For example, a unibody shaft stiffening device 300 such as the shaft stiffening device 300 shown in FIGS. 3A-3B and the a multiple component shaft stiffening device 300 such as the one shown in FIG. 6B as well as other various configurations of shaft stiffening devices 300 may be housed in a kit 700 such that the golfer may select a shaft stiffening device with the features most desirable to the golfer and most beneficial to the golfer's swing. Using the depicted kit 700 or other like kits consistent with that described herein, a golfer, golf professional or other users or distributers of golf equipment can fit a golfer with a particular shaft stiffening device 300.

Golf professionals are known to work with golfers to assist them in improving their golf game including their swing and associated play by analyzing the golfer's tendencies, providing instruction and recommendation regarding modifications to their swing and also in recommending various equipment including selection of clubs. Further, a golf professional for a certain golf manufacturer may offer a selection of features for which the golfer may select either alone, or with the assistance of the golf professional. Among the features that vary from golf club to golf club are various shaft characteristics including length, stiffness, kick point, a grip type, feel and many others. Each golfer may have a swing tendency that varies from other golfers. Accordingly golfers may desire and benefit from an individualized fitting of a golf club before such that the golfer's swing characteristics and swing tendencies may be noted and accounted for. In a fitting process, a golfer may have his or her swing analyzed by a professional either visually or by using any of various measuring and analysis devices known in the art and will be described further below.

FIGS. 8A-8C illustratively depict one manner of fitting a golf club 199 including a shaft 190. As is known, a golfer 10 may perform a number of swings in front of one or more golf professionals or golf club fitters. The movements including the golf swing may be viewed, recorded, and/or measured by a measuring device including a videographic device like a digital video camera. FIGS. 8A and 8B illustrate top plan and rear views respectively of a golfer swinging a golf club and hitting golf balls in an illustrative fitting station 1000. The fitting station 1000 may have any of a number of arrangements and features. The fitting station 1000 shown in FIGS. 8A-8C is an indoor fitting station. However, fitting stations 1000 may be indoor or outdoor and may be located at a driving range or other practice facilities, at a golf course including in or near a pro shop and various other locations as are known. The fitting station 1000 may include a hitting mat 1010, especially when the fitting station is an indoor station or when the station is part of a driving range. Although, a fitting station may occur on a grass tee box or other outdoor natural golf environment. Here, the indoor fitting station 1000 also includes a net 1030 that a golfer 10 may hit the ball into in performing his or her shots, practice swings and swings in front of a golf professional or golf club fitter. The net 1030 permits the fitting to be done in a more limited space such as indoors, in a pro shop or in a driving range with limited land available. Behind the net 1030 may be a background 1040 or other structures that may make the golfer feel as if he is on the golf course. Also, while not specifically depicted, the background may house or protect a further measuring device(s) including velocity or force sensors, videographic devices and other devices that may be utilized in the fitting of the golfer.

The ball travel of a golfer's shot may be monitored by watching an entire ball flight at a fitting station on a driving range that possesses sufficient space for the ball to travel until it comes to a natural stopping point/lie. Also, a golfer may also hit in a confined spaced monitored by a digital video camera or other computing devices that can determine the travel path based upon initial characteristics of the shot including velocity, trajectory, spin etc. Further measuring devices may be used to further understand the swing path and related tendencies of a golfer. In one example configuration, a golfer's swing may be filmed using a digital video camera device 1060. In particular the golfer's swing may be filmed from a toe end view such that the golfer has a stance square to and facing the camera. In another configuration, the golfer's swing my alternatively or additionally be filmed by a measuring device positioned at a position such as the position where measuring device 1061 is illustratively shown as being. By filming the golfer's swing from square orientations such as the rear and toe end, the video may be compared to images and swing paths performed and recorded by a golfer having preferred mechanics as is shown in FIG. 8C.

Among the devices and tests that may be used to monitor the swing path, contact orientation and related characteristics of a golfer swing are video recording, radar tracking including Doppler radar technology, motion detection devices, speed radar devices, ball flight tracking devices and monitoring systems and similar golf swing analysis devices as are known in the art. These measuring devices may be positioned as illustrative measuring devices 1060, 1061 are shown as being positioned. These devices may also be positioned in front of the golfer 10 such that the golfer is hitting at the measuring device or on the heel end side of the golfer behind the golfer's back. Even further, measuring devices may be placed overhead or practically anywhere such that the measuring devices can record data such as video images of the golfer's movements or track and record data or characteristics associated with the portions of the golf club or ball movement such as velocity, direction, orientation, and other characteristics as a re known. Other devices focused at determining the golf club's orientation during the swing and in particular the orientation of the golf club through the hitting zone when the golf club head strikes the golf ball may be utilized. These devices may be the same or similar devices as the videographic, radar or other motion tracking devices or the devices may be as simple as lie board devices which depict where a bottom surface of the golf club contacts the ground and the direction of movement and orientation of the club through the hitting zone. Also basic tape devices placed over the hitting surface 125 of a golf club head may be used to provide data regarding the portion of the hitting surface 125 where the golf ball is being hit to determine whether the ball is being hit in a sweet spot or off-center such that the swing or club may need adjustment to optimize results.

After a sufficient number of swings and “practice” or “sample” shots have been made to provide a desired sampling of shots to provide for a reliable fitting, the golf and/or fitting professionals can use the data collected to recommend a particular golf club head 100 housing a visual swing indicator 400 that will help the golfer performing a golf swing more regularly according to traditional preferred swing mechanics. Among the characteristics collected or measured may include swing path data, trajectory, orientation of the golf club on impact, ball spin, ball flight and physical dimensions and ergonomic characteristics of the golfer, to name just a few. The analysis of the swings including swing patterns can be used to determine a desired swing path, tendencies of the golfer's swing, and changes to the golfer's current swing path such that the specific changes required may be more visibly noticeable. The bend and flex characteristics may be determined and shown such that an analysis can be performed to determine whether a club shaft of a club is appropriate as maximizing the performance of a golfer with particular swing tendencies. For example, preferred stiffness, preferred location of kick point and effects of a shaft stiffening device located at certain locations.

FIG. 8C illustrates a display 1050 depicting two respective swing characteristics outputs 1051, 1052 illustratively depicting two swings of golfers in videographic form such as digital video. In one arrangement the displayed swing 1051 may be a videographic image of preferred swing of a professional golfer or other golfer including a “virtual golfer” with preferred swing mechanics. On the right, the golf swing 1052 may be an actual swing of a golfer 10 currently being analyzed in the fitting station 1000. Through the split screen comparison on display 1050, a golfer may be analyzed and fitted for a particular golf club features such as visual swing indicators, shaft characteristics, and alignment aides and other features to facilitate a golfer swinging in a preferred manner to achieve preferred performance. For example, backswing paths 1055A, 1055B of the golfers may be compared during the swings 1051, 1052. Likewise, the orientations of the golf club head 1056A, 1056B, the golfers' arm and hand positions 1057A, 1057B, and the head positions 1058A, 1058B may be compared visual. Other comparisons and analysis may be performed as is known. While the display 1050 here illustrates videographic information relating to the golfers' swings, the display 1050 may be utilized during other aspects of the analysis including output of various other characteristics utilized in fitting the golfer 10. Further, as shown in FIG. 8B the display 1050 may also be used to enhance the fitting experience and may be visible to the golfer during the fitting process. However, various configurations of outputs can be used to perform a swing analysis and provide output data relating to the golfer's swing to the golfer or the golf professional.

Illustrative aspects of the present invention are disclosed above and in the accompanying drawings with reference to a variety of embodiments. The purpose served by disclosure of the embodiments, however, is to provide an example of the various aspects embodied in the invention, not to limit the scope of the invention. One skilled in the art will recognize that numerous variations and modifications may be made to the embodiments without departing from the scope of the present invention, as defined by the appended claims. 

1. A golf club shaft stiffening device comprising: a flexible tubular body including an inner circumference and a length forming a tubular cavity, wherein the inner circumference is sized and configured to circumscribe and constrictively engage an outer surface of a shaft and to cause the shaft to have an increased stiffness characteristic.
 2. The golf club shaft stiffening device of claim 1, wherein the shaft stiffening device is configured for removable engagement with the shaft.
 3. The golf club shaft stiffening device of claim 1, wherein the flexible tubular body is a unibody member.
 4. The golf club shaft stiffening device of claim 1, wherein the shaft stiffening device is configured to cause a flex point of the shaft to be varied when the shaft stiffening device is constrictively engaged at different points along the shaft.
 5. The golf club shaft stiffening device of claim 1, wherein the flexible tubular body is specifically configured and sized to constrictively fit and be slidably adjustable within one of a low section, a mid section, and a high section of the shaft.
 6. The golf club shaft stiffening device of claim 1, wherein the flexible tubular body is specifically configured and sized to constrictively fit and be slidably adjustable within a high section of the shaft and wherein the flexible tubular body is configured such that an outer surface of the flexible tubular body is flush with an outer surface of a grip when an end of the tubular body abuts an end of the grip.
 7. The golf club shaft stiffening device of claim 1, wherein the flexible tubular body comprises one of a rubber, a plastic and a polymer.
 8. The golf club shaft stiffening device of claim 7 further comprising, an original shaft state and an engaged shaft stiffening device state in which a shaft stiffening device is constrictively engaged around a portion of the shaft, wherein the region of the shaft housed between two opposing ends of the shaft stiffening device has a higher stiffness in the engaged shaft stiffening device state than in the original shaft state.
 9. A golf club comprising: a golf club head; a shaft coupled to the golf club head and housing a grip; and a shaft stiffening device slidably housed on an outer surface of a shaft such that the shaft stiffening device is external to the shaft.
 10. The golf club of claim 9, wherein the shaft stiffening device includes a hollow tubular body with an inner circumference configured to constrictively engage the shaft across a length of the hollow tubular body.
 11. The golf club of claim 10, wherein an inner circumference of the shaft stiffening device continuously increases along the length from a first end of the hollow tubular body to a second opposing end of the hollow tubular body.
 12. The golf club of claim 10, wherein the hollow tubular body is sized and configured to constrictively engage one of a low section, a mid section, and a high section of the shaft, the length of the hollow tubular body being smaller than the length of the one of the low section, the mid section and the high section of the shaft.
 13. A method of fitting a shaft of a golf club with a shaft stiffening device comprising the steps of: determining a stiffness characteristic of a shaft of a golf club; determining a desired stiffness characteristic of a shaft based upon a swing of the golf club using a measuring device; and selecting a particular flexible tubular body shaft stiffening device from a plurality of available flexible tubular body shaft stiffening devices based upon the determined desired stiffness characteristic and applying the particular shaft stiffening device to the shaft by positioning the particular flexible tubular body shaft stiffening device on the shaft such that the inner circumference of the particular flexible tubular body shaft stiffening device constrictively engages an outer surface of the shaft.
 14. The method of fitting a shaft of a golf club with a shaft stiffening device of claim 13, further comprising the step of determining a desired flex point of the shaft.
 15. The method of fitting a shaft of a golf club with a shaft stiffening device of claim 13, further comprising the step of positioning the particular flexible tubular body shaft stiffening device at one of a low section, a mid section, and a high section of the shaft based upon the determination of the desired stiffness characteristic.
 16. The method of fitting a shaft of a golf club with a shaft stiffening device of claim 14, further comprising the step of positioning the particular flexible tubular body shaft stiffening device at one of a low section, a mid section, and a high section of the shaft based upon the determination of the desired flex point of the shaft.
 17. The method of fitting a shaft of a golf club with a shaft stiffening device of claim 15, further comprising the step of slidably adjusting the flexible tubular body shaft stiffening device within one of a low, mid, and high section of the shaft.
 18. A kit providing a series of shaft stiffening devices comprising: a first, a second and a third distinct shaft stiffening device, each of the first, the second and the third shaft stiffening devices including a hollow tubular body with an inner circumference, wherein the hollow tubular body and the inner circumference of the first, the second and the third shaft stiffening devices are respectively sized and configured for constrictive engagement of a low section, a mid section and a high section of a shaft of a golf club.
 19. The kit providing a series of shaft stiffening devices of claim 18, wherein the first shaft stiffening device is sized and configured to be slidably adjustable within the low section of the shaft of a golf club, the second shaft stiffening device is sized and configured to be slidably adjustable within the mid section of the shaft of a golf club, and the third shaft stiffening device is sized and configured to be slidably adjustable within the low section of the shaft of a golf club.
 20. The kit providing a series of shaft stiffening devices of claim 19, wherein each of the respective first, second and third shaft stiffening devices are composed of one of a rubber, a plastic and a polymer.
 21. The kit providing a series of shaft stiffening devices of claim 19, wherein each of the shaft stiffening devices is configured to increase a stiffness characteristic of the shaft of the golf club when in constrictive engagement with the golf club.
 22. The kit providing a series of shaft stiffening devices of claim 19, wherein each of the shaft stiffening devices is configured to provide a different flex point for the shaft of the golf club when in constrictive engagement with the golf club. 